A charged particle beam apparatus includes a semiconductor inspection apparatus such as a length measurement electron microscope to which a scanning electron microscope is applied. The semiconductor inspection apparatus controls an object point position of an objective lens with high accuracy in order to obtain a stable inspection result, and thus obtains an accurate display magnification. This is so that deflection sensitivity of a scanning deflector and an optical magnification of the objective lens which depend on an object point position of the objective lens are set with high accuracy.
On the other hand, the semiconductor inspection apparatus is required to irradiate a circuit pattern with an electron dose corresponding to the circuit pattern to be inspected. For example, in a length measurement electron microscope, a circuit pattern made of a resist material or the like is irradiated with an electron beam of several pA for the purpose of low damage, and a circuit pattern having a three-dimensional structure, such as a trench portion, is irradiated with an electron beam of several nA for the purpose of an increase of a signal amount.
Meanwhile, PTL 1 discloses a charged particle beam apparatus which can obtain an inspection result with good stability and reproducibility even in a case where inspection is performed by changing an optical condition (in a case where an electron dose is changed by using a set value for an electron gun power source). PTL 1 discloses that “a current limiting diaphragm 17 is disposed between a focusing lens 8 and a crossover position 10”, and “the excitation intensity of the focusing lens 8 is controlled so that a ratio between an amount of currents (Ip) applied to a sample 12 through the current limiting diaphragm 17 and a total current amount (Ia+Ip) is constant, and thus the crossover position 10 is constant”.
PTL 2 discloses a circuit pattern inspection apparatus which inspects a foreign substance on a wafer by using an electron beam in a manufacturing process of a semiconductor device. PTL 2 discloses a method in which a sample is scanned with an electron beam in a relatively small area, with a relatively small current, and at a relatively low speed, and discloses a method “in which aberration of an optical system, or a factor to hinder convergence of an electron beam, called an coulomb effect is minimized so that a minute beam is formed, by reducing an electron beam current more than when a defect detection inspection is performed, and thus a high resolution is obtained”, and “the method in which a magnification of the optical system is changed by changing a focal length of a lens, and thus an opening angle of a beam is reduced without moving a diaphragm”. PTL 2 also discloses that “it is possible to move a crossover position to a position over the diaphragm and also to improve a resolution by making the intensity of a condenser lens greater than when defect detection inspection is performed”, and “since b is smaller and c is larger than when defect detection inspection is performed, and thus a magnification is reduced; and an irradiation angle β can be reduced”.
PTL 3 discloses an electron beam exposure apparatus and an electron beam exposure method in which a variation in an electron beam is suppressed. PTL 3 discloses that “the electron beam 3 having passed through the shaping aperture 7 is incident to the projection lens 8; the projection lens 8 is driven by the projection lens craving unit 35; the projection lens 8 focuses the incident parallel electron beam 3; the focused electron beam 3 is formed at a crossover position; and the blanking aperture 10 is disposed at the crossover position, and the blanking electrode 9 is disposed between the projection lens 8 and the crossover position (that is, a position of the blanking aperture 10)”, and “in the example illustrated in FIG. 3, the current limiting aperture 5 is located between the crossover of the electron beam 3 and the irradiation lens 6, but the invention is not limited thereto, and may be located between the condenser lens 4 and the crossover of the electron beam 3”.